How Scientists Are Fighting Lead and Cadmium Pollution in Karangsong, Indonesia
Beneath the shimmering blue waters of Karangsong Port in Indramayu, Indonesia, an invisible threat accumulates—heavy metals that silently poison the marine ecosystem.
While this bustling port supports local livelihoods through fishing and trade, it simultaneously suffers from industrial pollution and waste that have transformed its sediments into a reservoir of toxic elements. Among the most concerning pollutants are lead (Pb) and cadmium (Cd), metals that don't break down but instead build up in marine organisms, eventually finding their way to humans through seafood.
Heavy metals can accumulate in marine organisms at concentrations thousands of times higher than in the surrounding water.
Consumption of contaminated seafood is the primary pathway for human exposure to marine heavy metals.
The situation in Karangsong represents a microcosm of a global problem. As we increasingly recognize the interconnectedness of human activities and environmental health, the story of Karangsong's contamination—and the scientific quest to address it—offers both warning and hope. Recent breakthroughs in bioremediation have opened promising avenues for cleaning these polluted waters using nature's own tools: specialized metal-eating bacteria.
Historically used in gasoline, paints, and various industrial processes, lead continues to contaminate marine environments through runoff and atmospheric deposition.
This metal enters marine systems primarily as a by-product of zinc refining, plastic production, battery manufacturing, and agricultural runoff from phosphate fertilizers.
The northern coastal area of Indramayu, where Karangsong is located, experiences multiple pollution pathways. Industries operating near the port, including manufacturing and oil companies, discharge waste containing these heavy metals. Additionally, agricultural activities inland contribute cadmium through fertilizer runoff that eventually reaches coastal waters through rivers and groundwater 3 . The situation is exacerbated by waste from fish auctions and other port activities, creating a complex pollution cocktail that settles in sediments.
Manufacturing and oil companies release waste containing heavy metals directly into the water system.
Phosphate fertilizers used in farming contain cadmium that washes into rivers and eventually reaches the coast.
Waste from fish auctions and shipping operations contributes to the pollution burden.
Airborne particles from industrial activities settle on water surfaces and add to contamination.
Confronted with the challenging and costly task of cleaning heavy metal pollution, scientists have turned to a remarkable natural solution: bioremediation.
This approach uses living organisms, particularly microorganisms, to remove or neutralize pollutants from contaminated sites.
The principle behind bioremediation is simple yet powerful. Some bacteria have evolved biochemical mechanisms that allow them to survive in metal-contaminated environments. These mechanisms include:
Where metals bind to the surface of bacterial cells
Where metals are transported into bacterial cells
Where bacteria convert toxic metals into less toxic forms
These metal-tolerant bacteria essentially eat the pollution, transforming dangerous contaminants into less harmful substances. While the concept has been applied to various pollution scenarios, its application to Karangsong's specific contamination profile represents an innovative approach to environmental restoration 6 .
In 2025, a team of researchers from Universitas Padjadjaran embarked on a crucial experiment to isolate and identify cadmium-reducing bacteria from Karangsong's contaminated sediments 3 .
Researchers collected sediment samples from approximately 50 cm above sea level in areas known to be contaminated with cadmium, using a piston core to reach 60 cm depth. These samples were immediately stored in sterile flasks and kept at 4°C to preserve the natural microbial communities.
In the laboratory, sediments were dispersed in distilled water and serially diluted. Aliquots of the dilution were spread onto Petri dishes containing nutrient agar (NA) medium dissolved in 100% natural seawater. The plates were incubated at 37°C for 24 hours, allowing bacteria to form visible colonies.
The genomic DNA of promising cadmium-reducing isolates was extracted using a Trisure Bioline Extraction kit. The researchers then amplified the 16S rRNA gene via Polymerase Chain Reaction (PCR) using universal primers. The PCR products were sequenced and analyzed using Bioedit software, then compared to known sequences in gene bank databases.
Isolates were inoculated in Nutrient Broth and exposed to varying concentrations of cadmium (1, 1.5, and 2 mg/L) for 18 hours. Bacterial growth was measured using a spectrophotometer to assess resistance.
To measure actual cadmium removal, isolates were introduced into filtered seawater solutions containing different cadmium concentrations (0.5, 1, and 1.5 mg/L). The reduction in cadmium levels was monitored at 0, 12, 24, and 48-hour intervals.
Both bacterial strains reduced cadmium levels by up to 50% within just 6 hours of treatment.
| Cadmium Reduction Capability of Bacterial Isolates | ||||
|---|---|---|---|---|
| Time Interval | Cd Concentration (0.5 ppm) | Cd Concentration (1.0 ppm) | Cd Concentration (1.5 ppm) | |
| 0 hours | 0.5 ppm | 1.0 ppm | 1.5 ppm | |
| 6 hours | 0.25 ppm | 0.5 ppm | 0.75 ppm | |
| 12 hours | 0.22 ppm | 0.45 ppm | 0.68 ppm | |
| 24 hours | 0.18 ppm | 0.38 ppm | 0.59 ppm | |
| 48 hours | 0.15 ppm | 0.32 ppm | 0.51 ppm | |
Data source: Pribadi et al., 2025 3
| Identification and Characteristics of Bacterial Isolates | ||||
|---|---|---|---|---|
| Isolate Code | Species Identification | Similarity Index | Morphology | Colony Color |
| Karangsong Cd 3 | Pseudoalteromonas issachenkonii strain KMM 3549 | 77.28% | Diplobacilli | Off-white |
| Karangsong Cd 7 | Pseudoalteromonas tetraodonis GFC strain IAM 14160 | 98.71% | Coccobacillus | Yellowish |
Data source: Pribadi et al., 2025 3
The dramatic reduction in cadmium concentrations demonstrated by these isolates highlights their potential as effective bioremediation agents. The researchers noted that the bonding of heavy metals in solution occurs through an ion exchange process on the bacterial cell wall, where naturally occurring ions are replaced by heavy metal ions 3 .
Conducting such sophisticated environmental research requires specialized materials and reagents.
| Reagent/Equipment | Primary Function | Application in Pollution Research |
|---|---|---|
| Graphite Furnace Atomic Absorption Spectrometry (GFAAS) | Detection and quantification of heavy metals | Measuring lead and cadmium concentrations in environmental samples 1 |
| Inductively Coupled Plasma Mass Spectrometry (ICP-MS) | High-sensitivity metal detection | Analyzing multiple heavy metals simultaneously in seafood and sediment samples 4 |
| Trisure Bioline Extraction Kit | DNA extraction from bacterial isolates | Obtaining genetic material for molecular identification of metal-resistant bacteria 3 |
| PCR Reagents and Primers | DNA amplification | Copying specific gene segments (like 16S rRNA) for bacterial identification 3 |
| Nitric Acid (HNO₃) and Hydrogen Peroxide (H₂O₂) | Sample digestion | Breaking down organic matrices in environmental samples prior to metal analysis 4 |
| Nutrient Agar/Broth | Bacterial culture medium | Growing and maintaining bacterial isolates for experimentation 3 |
| Certified Reference Materials | Quality assurance | Verifying accuracy of metal concentration measurements 4 |
These specialized tools enable scientists to detect minute quantities of heavy metals—sometimes at parts per billion levels—and develop innovative solutions to environmental pollution problems.
The discovery of cadmium-reducing bacteria in Karangsong's sediments offers genuine hope for innovative pollution management. The remarkable ability of these indigenous bacteria to cut cadmium levels by half in just hours suggests that bioremediation could be a viable, natural solution for this contaminated ecosystem. Rather than introducing foreign organisms, using bacteria already adapted to Karangsong's specific conditions presents a more sustainable approach to environmental restoration.
However, cadmium is only part of the pollution picture. While the 2025 study focused on cadmium, we must remember that lead contamination also threatens Karangsong's waters. The same principles of bioremediation could potentially be applied to lead pollution, though different bacterial species might be required.
The global significance of this research cannot be overstated. As noted in a comprehensive ten-year analysis of seafood contamination, heavy metals like cadmium, lead, and mercury continue to pose health risks through seafood consumption, with certain species like swordfish and sharks showing particularly high mercury levels 4 . The lessons from Karangsong could thus inform remediation strategies worldwide.
For the residents of Indramayu and similar coastal communities, effective bioremediation could mean safer seafood, healthier ecosystems, and more secure livelihoods.
As research progresses, these microscopic cleanup crews may play an outsized role in reversing human-caused pollution, proving that sometimes the best solutions come from the very environments we seek to protect.
The story of Karangsong's pollution is still being written, but with continued scientific innovation and commitment to environmental stewardship, its next chapters may tell of recovery and resilience—a testament to nature's capacity to heal when given the right tools.